What is Grimmering?
1.
An unwanted person listening in to and jumping in on your conversation
Person #1- "So hey what are you doing this weekend?"
Person #2- "Probably grab a couple a beers and watch the game."
Unwanted Person#3 (listening over your shoulder)- "Sounds fun what time are we gonna meet up?"
Persons #1 and 2 say "stop the grimmering man."
See